A DVD ISO image is a file that contains the contents of a DVD, including the video, audio, and data tracks. It's essentially a snapshot of the DVD's file system.
Your Activation Key is invalid
There are a couple reasons why this might have happened:
1) you don’t have an activation key and entered a fake one
2) you entered the wrong code
3.) You didn't sign up properly
Please double-check that you have downloaded your activation key according to the instructions in the tutorial video.